6. Communications and Networking Flashcards
1
Q
What does LAN stand for?
A
Local Area Network
2
Q
What is a LAN?
A
A collection of computers and peripheral devices connected together on a single site.
3
Q
Give an example of a LAN.
A
A school is likely to have a LAN.
4
Q
What are the advantages of networking stand-alone computers into a LAN?
A
- Sharing resources - Files, peripheral devices, Internet connection
- Communication - Email, Messaging systems, File transfer
- Centralised management - Profile and security management, Software distribution, Users can access their files on any PC, Centralised back-up
5
Q
How does connecting stand-alone computers into a LAN allow sharing of resources?
A
- Sharing folders and files
- Sharing peripheral devices
- Sharing an Internet connection
6
Q
How does connecting stand-alone computers into a LAN allow communication?
A
- Chat systems
- File transfer between computers
7
Q
How does connecting stand-alone computers into a LAN allow centralised management?
A
- User profiles and security can be managed centrally
- Software can be distributed across the network instead of installing on each individual computer
- Users can use any PC but still see their own files
- Centralised backup of all files
8
Q
What are the main network topologies?
A
- Ring
- Bus
- Star
9
Q
What is a topology?
A
A description of how devices are connected together in a network.
10
Q
Describe a bus network.
A
- Computers connected to a single backbone (called the bus), ended by terminators
- Only one computer can transmit at any one time
11
Q
What are the advantages and disadvantages of a bus network?
A
ADV
• Easy and inexpensive to install -> Less cabling
• Easy to add new computers
DIS
• If main cable fails, then whole network goes down
• Cable failures are hard to isolate because all of the computers in the network are affected
• Performance slows down as the traffic increases
12
Q
Describe a ring network.
A
- Computers connected to adjacent computers in a ring
- Computers take turns to transmit, controlled by passing a token around. Computers can only transmit when they have the token.
- Transmission all in one direction
13
Q
What are the advantages and disadvantages of a ring network?
A
ADV
• Not dependent on central computer (like a star network is)
• Token passing is simple and reliable
• Consistent performance, even with a lot of traffic
DIS
• Single node or link failure disrupts the entire network
14
Q
Describe a star network.
A
- All computers have their own cable connecting them to central computer
- The central computer controls the network and is usually a switch or server
15
Q
What are the advantages and disadvantages of a star network?
A
ADV
• If one cable fails, only one station is affected
• Consistent performance, even with heavy use
• Easy to add new computers
• More secure -> Messages from computer go directly to centre
DIS
• Expensive due to cabling
• If the central computer fails, the whole network goes down
16
Q
What can be found at the centre of a star topology?
A
A switch or server (or a hub)
17
Q
Describe how computers in a school might be connected in a LAN.
A
- Computers in a classroom connected by a star topology to a hub or switch (wired or wirelessly)
- Different classroom topologies linked by a star or bus topology
18
Q
How does the size of a LAN determine what is at the centre of a star topology?
A
- Small network -> Server
* In a room which is part of a larger LAN -> Switch
19
Q
What does NIC stand for?
A
Network Interface Card
20
Q
What is a Network Interface Card (NIC)?
A
- The card that plugs into a computer to provide a connection to a LAN.
- Can be wireless or cabled.
- Holds the MAC address.
21
Q
What allows a computer to connect to a LAN?
A
The Network Interface Card (NIC).
22
Q
What is a server?
A
A computer designed to process requests and deliver data to other client computers over a local network or the internet.
23
Q
What is a stand-alone computer?
A
One not connected to any other.
24
Q
What is a network?
A
The term for two or more computers connected together.
25
What is peer-to-peer network?
A method of organising a network where:
• Devices are all of equal status rather than having specialised roles
• Each computer can access resources on another computer
• Each computer can act as a client or server at times
26
What is a client-server network?
A method of organising a network where:
• Some computers act as servers
• The computers (clients) make requests to these servers
• Management of the server is centralised at the server
27
Why might a peer-to-peer network be used instead of a client-server network?
If the office or network is small, the it is not cost-effective to run a client-server network.
28
Can any computer access files from any other computer on a peer-to-peer network?
Yes, as long as access rights have been granted.
29
What are the advantages of a peer-to-peer and client-server network?
```
PEER-TO-PEER
• Easy to set up and maintain
• No dependency on server
CLIENT-SERVER
• Centralised security and management
• Back-up can be done from central server
```
30
What does WAN stand for?
Wide Area Network
31
What is a WAN?
A collection of computers and networks connected together over a geographically remote area (several sites).
32
Give an example of a WAN and explain why this is a WAN.
The Internet - it is a network of interconnected networks.
33
What does PAN stand for?
Personal Area Network
34
What is a PAN?
Usually a temporary wireless connection using a protocol like Bluetooth.
35
Give an example of a PAN.
The Bluetooth connection between two phones.
36
Do networks connected by a WAN need to be miles apart?
* No, it is not about distance. It is more about what is inbetween the two sites.
* For example, a highway that splits a campus will mean that the two LANs on either side will have to be connected by a WAN.
37
How can LANs be connected to make a WAN?
The school or business which owns them has to use hired infrastructure, which they have to rent from a network service provider.
38
What is a protocol?
A set of rules that defines how devices communicate.
39
Give some examples of protocol.
IP, HTTP, HTTPS
40
What things will a protocol cover?
* How the transmission will start (getting attention of the other computer)
* The transmission speed
* The significance of bits being transmitted
* How the bits will be delivered
* Error-checking procedures
41
What does IP stand for?
Internet Protocol
42
What is IP?
* The protocol used on the Internet, by which all computers, servers and routers communicate.
* It is used to find a route for messages through a network.
43
What holds the MAC address?
The Network Interface Card (NIC)
44
What is the MAC address?
* A unique hardware number allocated to every NIC.
| * It allows messages to be transmitted between devices in a LAN (it works like an address on a letter does)
45
Can the MAC address on a NIC be changed?
No, it is hard-coded into the NIC.
46
How long is a MAC address?
48 bits, which is written as 12 hex digits.
47
What is a message?
A communication between devices, which is split into packets for sending across the network and put back together on the other end.
48
What is a packet?
A fixed sized part of a message which is sent across a network.
49
What are the parts of a packet being sent over LAN?
* Header with MAC address of receiver
| * Payload (the actual content)
50
What is the Internet?
A public worldwide network of computers and networks, interconnected by a verity of communication links.
51
What is an interface?
A way of connecting two devices.
52
Does a Network Interface Card allow transmission wirelessly or through wires?
Both
53
What wires are usually used in LAN networks?
* UTP (Universal Twisted Pair) cables
| * Fibre optic cables
54
What does a repeater do?
Regenerates and re-sends a weak signal.
55
What does a hub do?
It connects together computers and servers on a network. It sends signals from a computer to all the others by repeating the signal.
56
What does a switch do?
It connects together computers and servers on a network. It sends signals from a computer to a specific one by repeating the signal. It is able to direct the signal to the correct receivers.
57
What is the difference between a hub and a switch?
They are very similar in that they send signals along a network. However, a switch is able to direct the signal to the correct receiver, while a hub just repeats the signal to all of the receivers.
58
How does a switch work?
* It stores the MAC addresses of devices on the network
| * It filters data packets to see which devices have asked for them
59
What is a wireless access point?
* The device to which a computer connects wirelessly.
| * It can be a wireless hub or wireless switch.
60
Which device is required to connect a network to the Internet?
* Modem
| * Router
61
What is the Internet actually made up of?
* Routers - these are much bigger and higher performance than those at school or at home.
* They form the backbone and IP is the protocol used between them.
62
What unique labels are used to differentiate between individual devices in a LAN and on the Internet?
* LAN -> MAC address
| * Internet -> IP address
63
What is an IP address?
A method of labelling any device connected to the network with a unique numerical value.
64
Describe what an IP address looks like.
* 4 numbers separated by dots
| * Each number is between 0 and 255
65
What is the range of each number in an IP address and why?
Between 0 and 255 because each one represents a byte.
66
What will a packet being sent over the Internet contain?
* Sequence number
* IP address of receiver
* IP address of sender
* Payload (the actual content)
67
What protocols are used on the internet?
* IP - Internet Protocol
| * TCP - Transport Control Protocol
68
What does TCP stand for?
Transport Control Protocol
69
What is TCP?
The way of splitting messages into packets and ensuring they arrive at their destination.
70
Where are websites stored?
On web servers connected to the internet.
71
Do websites have an IP address?
Yes
72
Describe the process of packet switching.
* Message is split up into packets by TCP
* Packets travel from router to router over the Internet according to IP protocol
* TCP protocol reassembles the packets into the original message at the destination
73
How does IP allow efficient transmission of messages across the Internet?
At each router, the IP protocol decides which way to send the packet. Each router knows where the messages came from and the destination, so it can decide the most efficient path for each packet depending on traffic conditions.
74
What is a sequence number?
The number of a packet in the sequence of packets a message is broken down into.
75
Why is the sequence number important?
Due to traffic conditions, each packet may be sent a different way along the Internet, meaning that they need to be put together in the correct order on arrival.
76
What is Wi-Fi short for?
Wireless Fidelity
77
What is Wi-Fi?
A protocol that carries wireless network signals.
78
What is Internet working?
Where multiple networks are connected.
79
What is a translation gateway?
A way of translating from one network protocol to another.
80
What does ISP stand for?
Internet Service Provider
81
What does DNS stand for?
Domain Name System
82
What is a domain name?
The text label for a website in the internet, which corresponds to an IP address for that site.
83
What is a router?
* The hardware devices that make up the backbone of the Internet as well as providing connectivity from LAN to the internet.
* They use IP to communicate.
84
What is a DNS server?
A database of domain names and associated IP addresses stored on servers.
85
How many DNS servers are there?
Many - they frequently update each other on changes.
86
What are the advantages of using DNS servers to translate domain names into IP addresses?
* Humans doth have to remember or type in numerical addresses
* If the IP address changes at some point, the DNS servers can update their databases and the users can continue using the same domain name
* Many distributed DNS servers mean everyone has access to all addresses from their local DNS server
87
In most browsers, can both the domain name and IP address of a website be typed in in order to find it?
Yes
88
What does HTTP stand for?
HyperText Transfer Protocol
89
When might a device not be given a globally unique IP address?
When it is inside a private network. For example, you might not want anyone to be able to print to your personal printer. Therefore, the network as a whole is given an external IP address, but uses private IP addressing inside the network.
90
What happens if a DNS server does not contain the reference you were looking for?
It will search other connected DNS servers.
91
What is the advantage of an IP routing system?
A given router only needs to know where its neighbours are rather than where everything on the whole network is.
92
What is HTTP?
The protocol used by a browser to send page requests to a server and also by the server to send back the required page.
93
What is HTTPS?
A secure version of HTTP where transmissions are encrypted.
94
What is the difference between HTTP and HTTPS?
HTTPS is a secure version of HTTP.
95
What is the difference between HTTP and IP?
IP is used for transmissions between routers and devices, while HTTP is an end-to-end protocol between the PC and the web server.
(See diagram Pg 93 of textbook)
96
What are the two ways of connecting a network to the Internet?
* Modem
| * Local router
97
What is a digital signal?
A transmission signal that is made up of separate values (numbers).
98
What is an analogue signal?
A transmission signal that is continuously changing.
99
What things use a digital and analogue signals?
Digital: Computers and Internet
Analogue: Telephone Network
100
What is modem short for?
Modulator-Demodulator
101
What is a modem?
The hardware device used to convert the digital transmission from a computer into an analogue signal that can be carried over the telephone network. (And the vice versa on the other end)
102
Describe how a modem can be used to connect a network to the internet.
* Computer uses digital signals
* Modem converts these to an analogue signal
* Analogue signal sent down telephone network
* Modem converts these to a digital signal
* This travels through the Internet
103
What are the advantages and disadvantages of using a modem to connect to the internet?
```
ADV
• Cheap
DIS
• Slow
• Can't use phone and Internet at the same time
```
104
What is the more common way of connecting a computer to the internet?
A local router.
105
How many routers are needed to connect all the PCs in a home to the internet?
Just one. If the computers are connected in a LAN, they can share the router.
106
How can a local router be connected to the Internet?
* The fibre-optic cable that delivers your cable TV service.
| * The part of the phone line that connects your home to the local exchange using broadband technology.
107
Is connecting to the internet using a modem the same as using a router and part of a phone line?
No, both use a local cable, but the router method uses digital transmission all the way and phones and computers can be used simultaneously.
108
What is broadband?
* A digital method of connecting to the Internet that allows more than one transmission at a time.
* It may use the site's normal phone line or a fibre optic cable
109
What is WWW?
World-Wide Web - A collection of pages distributed on servers connected to the Internet. Uses HTTP to request and send pages to browsers.
110
What are the advantages and disadvantages of using a router to connect to the Internet?
```
ADV
• Faster
• 1 router can connect whole network
DIS
• Cheaper
• More than 1 signal can be transmitted at a time
```
111
What does HTML stand for?
Hyper Text Markup Language
112
What is HTML?
* The programming language used to define the layout and content of a webpage.
* Uses tags in conjunction with CSS to control how content is displayed
113
What is CSS?
Cascading Style Sheet - Defines the formatting and layout of content defined by HTML code.
114
What are tags?
Labels that go around the content to define the page layout.
115
How can a website be published to the Internet?
* Uploading it to your own web server
| * Uploading it to someone else's web server -> Hosting
116
What is web hosting?
Uploading a web site to someone else's web server.
117
What are the three types of network security?
1. Preventive measures
2. Detective measures
3. Corrective measures
118
In network security, what are preventive measures?
Measures aimed at stopping a hazardous event occurring.
119
In network security, what are detective measures?
Measures aimed at detecting when data has been corrupted or systems have been compromised.
120
In network security, what are corrective measures?
Measures aimed at correcting or restoring the system after problems have occurred.
121
Give some examples of preventive network security measures.
* Access rights
* Firewalls
* Physical security -> E.g. Locking rooms
* Passwords
* Encryption
* Acceptable use policy
122
Give some examples of detective network security measures.
* Virus checking software
* Firewall software
* Fire alarms
* Audit trials
123
Give some examples of corrective network security measures.
* Backup and restorative procedures
* Redundant hardware / Failover
* Disaster recovery procedures
124
What are user access levels?
A network policy that defines which users can see which folders and files and the type of access they have to them.
125
What is encryption?
Where the data is changed using a key before it is transmitted so that it can only be deciphered by another device with the appropriate key.
126
What is an acceptable use policy?
An agreement that computer users will sign/agree to before being allowed access to a computer of the network.
127
What is backing up?
Making a copy of files and folders in case they become lost or damaged.
128
What are some network policies?
* Backup and restore procedures
* Archiving
* Disaster recovery
* Failover
* Acceptable use
129
Describe backup and restore procedures.
Backups are normally made by:
• Using a removable hard disk or cassette tape
• Cloud backup services
130
What is the need for backup and restore procedures?
A backup is made in case of files getting corrupted or deleted.
131
Describe archiving procedures.
Data is taken off the main system and stored, usually on magnetic tape.
132
What is the need for archiving procedures?
There may be a large amount of data on a system which is no longer needed on a regular basis, but cannot be deleted, e.g. for legal reasons. This frees up space on the system.
133
What is the difference between archiving and backup procedures?
Backup involves making a copy of all relevant data, whereas archiving is taking the no longer necessary data without making a copy.
134
Describe disaster recovery procedures.
Disaster recovery plans include:
• Data being backed up
• Duplicate hardware systems being available very quickly
• A plan to restore backup data onto the new hardware
135
What is the need for disaster recovery procedures?
Some companies would be unable to operate without a computer system. Therefore, they have to have a plan in case of a fire, tidal wave, etc. so that they can get their system running again quickly.
136
What is failover?
When a hardware component fails, the computer switches over to a redundant component without service to the user being interrupted.
137
What does redundant mean?
* Spare, ready to be used if another component fails.
| * Relates to spare hardware components in fault-tolerant and failover systems that use failover.
138
What does fault-tolerant mean?
* A system that has been designed to cope with hardware failures.
* Uses redundant hardware and failover usually.
139
What is a backup?
* A copy of data taken from a live computer system as a precaution against system failure or corruption/deletion of files.
* To be restored in the event of data loss.
140
What is archiving?
Files are removed from the main computer system but kept in long-term storage, just in case they are needed in the future or because the law requires they be kept.
141
What is disaster recovery?
A collection of precautions that ensures the computer sheets, can be reestablished very quickly after a catastrophe.
142
Describe failover procedures.
Using a system with many spare (redundant) components, which can quickly switch to those if necessary.
143
What is the need for failover procedures?
If a computer system is mission-critical, it cannot be offline at all. It needs to have redundant components so it can switch to they instantly when needed.
144
Describe acceptable use policies.
Employees at a company sign a document to say that they will only use the system for appropriate things.
145
What is the need for acceptable use policies?
It prevents users accessing files they shouldn't and using the system for their own use.
146
What is compression?
Making files smaller for quicker transmission over a network.
147
Why do files need to be compressed?
It takes less time to transmit smaller files over the Internet.
148
What is lossy compression?
A data encoding method where files are compressed by removing some of the detail.
149
What is lossless compression?
A data encoding method where files are compressed but no data is lost.
150
When is lossy and lossless compression used?
Lossy: Pictures, Audio, Video
Lossless: Text, Data
151
What is truecolor?
Picture representation using 24 bits per pixel where the colours are RGB.
152
What is run length encoding?
Compressing an image by storing lengths of a single colour rather than individual pixels.
153
Give an example of a lossless compression technique.
* Run length encoding
* Dictionary compression
* Using fewer bits per pixel
154
What are the different image file types by their compression type?
```
UNCOMPRESSED
• Bitmap (.bmp)
LOSSLESS
• Portable Network Graphic (.png)
• Graphic Interchange Format (.gif)
LOSSY
• JPEG (.jpg)
```
155
What is the bitmap (.bmp) compression type?
Uncompressed
156
What is the potable network graphic (.png) compression type?
Lossless
157
What is the JPEG (.jpg) compression type?
Lossy
158
What is the graphic interchange format (.gif) compression type?
Lossless
159
Compare the colour depth of different image file types.
Bitmap - Uncompressed
PNG - 24 bits
JPEG - 24 bits
GIF - 8 bits
160
What is JPEG usually used for and why?
Photographs, because it has good colour depth (24 bits).
161
What is GIF generally used for and why?
• Images with large areas of solid colour
• Web graphics
Because GIFs have a smaller colour depth (8 bits), so they are smaller.
162
How does JPEG and GIF compression work?
• Although JPEGs have a higher colour depth than GIFs, they are compressed by losing data where it is unlikely to be noticed. • GIFs have a smaller file size because they only use 8 bits instead of 24.
163
What are the different video file types by their compression type?
LOSSY
• MPEG-1 (.mpg)
• MPEG-2 (.mp2)
164
What is the difference between MPEG-1 and MPEG-2?
* MPEG-1 is lower quality, suitable for small, low-resolution videos on CD
* MPEG-2 is higher
165
What are the different audio file types by their compression type?
```
LOSSLESS
• QuickTime (.mov)
LOSSY
• Windows Media Player (.wmv or .wav)
• MP3 (.mp3)
```
166
What is the smallest audio file size and what is it used for?
MP3 - Designed for downloading music from the Internet.
167
Remember to revise network hazards and their prevention.
Pg 102 of textbook.
